The fundamental difference between quick-frozen food and food frozen in your own refrigerator is that the time it takes for the food to complete freezing is different.
The essence of quick-frozen food lies in the word "speed". Quick-frozen food is pre-processed food that quickly passes through the maximum ice crystal zone of -1℃--5℃ within 30 minutes, and then is stored and transported in an environment below -18℃. Due to the fast cooling speed, the "ice crystals" formed are very small, so small that they will not seriously damage the food cells, so the flavor and nutrition of the food can be retained to the greatest extent.
Food frozen in your own refrigerator usually takes 2 hours to pass through the maximum ice crystal zone of -1℃--5℃. Relatively speaking, the ice crystals in food are larger, so during the thawing process, the ice crystals will pierce the cell structure of the food, destroying the flavor and nutrition of the food.
02. Quick-frozen products usually have a longer shelf life. Is it because preservatives are added?
In fact, the biggest advantage of quick-frozen food is that it can be stored for a long time without any preservatives. There are two reasons. On the one hand, microorganisms can hardly reproduce under low-temperature freezing conditions. On the other hand, by freezing most of the free water in the cells at low temperatures, the water activity in the food is reduced, the physical and chemical activities inside the food are slowed down, and the nutrients in the food are not easy to oxidize and deteriorate.
03. Many frozen fruits and vegetables are bright in color. Is it because of the addition of colorants?
At room temperature, the color of fruits and vegetables usually becomes dim as the storage time increases. The main reason is that the natural pigment substances in fruits and vegetables are oxidized. Frozen fruits and vegetables are generally processed with fresh fruits and vegetables of the season. After blanching and heating, they are quickly frozen immediately. The blanching and heating itself can make the oxidase in fruits and vegetables inactive. This treatment makes these natural pigments less likely to be oxidized, so it can "lock" the original bright color of fruits and vegetables, and there is no need to use colorants.
04. Is there a lot of nutrient loss after food is frozen?
Processed foods that have been rapidly frozen have little nutrient loss. In addition, storage at a low temperature of -18℃ can keep the nutritional value of food in a relatively ideal state.
05. Are frozen fruits and vegetables much less nutritious than fresh ones?
Studies have shown that frozen fruits and vegetables have little difference in nutritional value compared to fresh ones, and may even have higher nutritional value than some fresh ones. Because fresh fruits and vegetables need to be transported for several days after being picked before they can reach the kitchen, especially when these fruits and vegetables are fully exposed to heat and light, many vitamins and antioxidants will be lost during transportation. Of course, if fresh fruits and vegetables are delivered to consumers as soon as possible through the cold chain, their nutritional loss will be very small.
06. Will the nutritional value of frozen foods change after repeated freezing?
The answer is yes. When frozen foods are thawed for the first time, some ice crystals in the food will pierce the cells, and the water in the cells will flow outward, causing those nutrients that are easily soluble in water to be lost. When frozen again, larger ice crystals are usually formed, and these ice crystals will cause greater damage to the cells, and when thawed again, a lot of nutrients will be lost. At the same time, since the bacteria contained in the food will multiply in large numbers during the thawing process, accelerating the spoilage of the food, frozen foods cannot be frozen repeatedly, whether from the perspective of nutritional value or food safety.
07. What are the key points for selecting frozen food?
Go to regular supermarkets and stores and buy products produced by qualified companies; pay attention to the production date, shelf life and Sc mark of the product; the product packaging should be sealed and intact; the product surface should be shiny and without a large amount of ice crystals; touch the surface of the product, it should feel hard and not soften; meat and poultry products should not have a large amount of blood clots or ice cubes. At the same time, you should also carefully check the nutrition information table on the pre-packaged food label to see the fat and salt content in it to decide how much you should eat when eating to avoid nutritional imbalance.
